Hip joint socket

Abstract

A hip joint socket includes a plastic socket member and an outer metallic ring member laterally closely enclosing the socket member. The socket member has a conically shaped outer surface in closely fitting engagement with a corresponding conically shaped inner surface on the ring member. Outwardly projecting parts on the socket member fit in a dovetail fashion in corresponding recesses formed in the ring member. The socket is self-fixing within the ring member during any cold flow of its plastic material so that relative movement between the socket member and the ring member is prevented.

I claim: 
     
       1. A hip joint socket for cement-free anchoring in the pelvis, comprising a rigid outer member, and a socket member secured within said outer member, said outer member and said socket member each having a central axis and a first side and a second side extending transversely of the central axis with said first and second sides of each being disposed in spaced relation relative to the central axis, said first sides of said outer member and socket member being disposed in approximately the same plane and said socket member forming a socket therein having an opening located in the plane containing said first side of said socket member, said outer member being ring-shaped with a radially outer surface and a radially inner surface both extending around the central axis and between the first and second sides thereof, said outer surface tapering inwardly in the direction from the first side toward said second side, ribs formed in said outer surface extending transversely of the central axis of said outer member, said inner surface being conically shaped and tapering inwardly in the direction from the first side toward the second side, said socket member having an outer surface extending between said first and second sides thereof with said socket member outer surface being conically shaped and tapering inwardly in the direction from the first side toward the second side of said socket member, wherein the improvement comprises that at least three recesses are formed in said inner surface of said ring member, said recesses being a dove tail shape groove extending radially and substantially in a direction of the longitudinal axis of said socket, and wherein said socket member having a complementary outwardly extending ribs formed on said outer surface thereof so that said socket member is fitted in said outer member so that said socket member cannot rotate relative to said outer member. 
     
     
       2. A hip joint socket, as set forth in claim 1, wherein said outwardly extending ribs have a dimension in the direction between the first and second sides of said socket member less than the corresponding dimension of said recesses extending inwardly from the side of said outer member, leaving play in the axial direction. 
     
     
       3. A hip joint socket, as set forth in claim 1 or 2, wherein four recesses are formed in said ring member. 
     
     
       4. A hip joint socket, as set forth in claim 1 or 2, wherein said ring member is formed of pure titanium and said socket member is formed of polyethylene. 
     
     
       5. A hip joint socket, as set forth in claim 1 or 2, wherein said radially outer surface of said outer member is spherically shaped. 
     
     
       6. A hip joint socket, as set forth in claim 1 or 2, wherein said ribs on the outer surface of said outer member are constructed as double pitch threads. 
     
     
       7. A hip joint socket, as set forth in claim 6, wherein said threads have a slope of 4 to 6 mm. 
     
     
       8. A hip joint socket, as set forth in claim 7, wherein said threads have a slope of 4.5 to 5.5 mm. 
     
     
       9. A hip joint socket, as set forth in claim 7, wherein said threads have a height in the range of 2 to 4 mm. 
     
     
       10. A hip joint socket, as set forth in claim 9, wherein said threads have a height in the range of 2.5 to 3.5 mm. 
     
     
       11. A hip joint socket, as set forth in claim 6, wherein said double pitch thread is provided with axially cutting grooves.